Synthesis
of Stable Nanographenes with OBO-Doped Zigzag
Edges Based on Tandem Demethylation-Electrophilic Borylation

A tandem demethylation-aryl
borylation strategy was developed to
synthesize OBO-doped tetrabenzo­[<i>a,f,j,o</i>]­perylenes
(namely “bistetracenes”) and tetrabenzo­[<i>bc,ef,kl,no</i>]­coronenes (namely “peritetracenes”). The OBO-doped
bistetracene analogues exhibited excellent stability and strong fluorescence,
in contrast to the unstable all-carbon bistetracene. Single-crystal
X-ray analysis for OBO-doped bistetracene revealed a twisted double
[5]­helicene structure, indicating that this synthesis is applicable
to new heterohelicenes. Importantly, cyclodehydrogenation of the bistetracene
analogues successfully produced the unprecedented heteroatom-doped
peritetracenes, which opened up a new avenue to periacene-type nanographenes
with stable zigzag edges.